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Publication numberUS5322651 A
Publication typeGrant
Application numberUS 08/041,975
Publication dateJun 21, 1994
Filing dateApr 2, 1993
Priority dateApr 3, 1992
Fee statusPaid
Also published asDE69306152D1, DE69306152T2, EP0564354A1, EP0564354B1
Publication number041975, 08041975, US 5322651 A, US 5322651A, US-A-5322651, US5322651 A, US5322651A
InventorsGerard Emmer
Original AssigneeSidel
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and apparatus for the thermal treatment of thermoplastic preforms
US 5322651 A
Abstract
Preforms are thermally treated in a continuous-run oven equipped with infrared lamps. The portions of the oven exposed to infrared radiation are cooled by an air flow, whose temperature is kept constant by mixing air at ambient temperature with hot air. The latter is obtained by recycling at least part of the cooling air flow, which becomes heated as it carries away excess heat. A recycling mechanism in the form of a plenum box 13 equipped with a pivotable shutter 16 for adjusting the proportions of recycled hot air and ambient temperature air makes it possible to keep the temperature of the cooling air constant.
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Claims(4)
I claim:
1. A process for the thermal treatment of preforms made of thermoplastic materials for the manufacture of hollow bodies by blow molding or stretch blow molding, comprising the steps of: rotating the preforms about axes thereof and simultaneously conveying the preforms in front of infrared radiation heating elements, directing a flow of cooling air over the preforms and heating elements to draw away excess heat generated by the infrared radiation, and maintaining the temperature of the flow of cooling air constant and equal to a reference temperature set in advance by mixing air at ambient temperature and heated air, said heated air being obtained by recycling the flow of cooling air which has become heated from evacuating the excess heat, and the reference temperature being maintained by varying the proportions of air at ambient temperature and of recycled heated air in the mixture.
2. A process according to claim 1, wherein the reference temperature is equal to the maximum value reached by the ambient temperature during a given time period.
3. A process according to claim 2, wherein the time period covers a range of from one day to one year.
4. A process for the thermal treatment of preforms made of thermoplastic materials for the manufacture of hollow bodies by blow molding or stretch blow molding, comprising the steps of:
a) conveying the preforms past infrared radiation heating means, and simultaneously therewith rotating the preforms about longitudinal axes thereof,
b) directing a flow of cooling air over the heating means, said cooling air comprising a mixture of ambient temperature air and recycled cooling air heated by the heating means,
c) establishing a reference temperature for the cooling air,
d) sensing the actual temperature of the cooling air,
e) comparing the actual and reference temperatures to determine a difference therebetween, and
f) varying the proportions of ambient temperature air and recycled cooling air in accordance with said difference to maintain the actual cooling air temperature constant and equal to the reference temperature.
Description
BACKGROUND OF THE INVENTION

This invention concerns, in general, ovens which heat by infrared radiation, and, more specifically, ovens designed to heat preforms made of thermoplastic materials for the manufacture of hollow bodies such as bottles, flasks, or similar objects by blow molding or stretch blow molding.

Conventional machines used to manufacture these hollow bodies by blow molding or stretch blow molding; incorporate at least a preform thermal treatment station, in which the preforms are heated to a temperature such that they can then be molded in a blow molding or stretch blow molding; operation and a station for blowing the preforms in molds whose impressions have the shape of the hollow bodies to be produced. Respective conveyors provide for the feed of the preforms to the thermal treatment station and the transfer of the heated preforms between the treatment station and the blowing station.

Heating by infrared radiation is conventionally known and widely used in the industry for the thermal treatment of plastic preforms, in particular those made of polyethylene terephthalate (PET), the preforms being designed for the manufacture of hollow bodies such as bottles. In comparison with other heating or thermal treatment methods such as convection and conduction, and considering the low level of thermal conductivity of the material, heating using infrared radiation gives advantageous output and allows increased production rates.

Given the high energy density given off in these ovens, it is necessary to cool the parts of the oven most exposed to infrared radiation, in particular the stationary parts, in order not to damage them. To this end, a flow of cooling air which carries away excess calories has become necessary. In conventional installations, air is collected in the premises on which the oven is installed, using one or more fans. Once thermal exchange has been achieved, this air is evacuated within the premises at the top part of the oven.

The search for ever-increasing rates of production, the blowing of bottles or containers having increasingly complex shapes, and reducing the weight of the preforms while preserving, and indeed enhancing, the technical performance of the finished articles, require a distribution of material in the final product which is both precise and accurately repeated during the entire production run. These requirements make it necessary to control completely the thermal treatment of the preforms, thereby requiring precise adjustments regulating the heating profile. A very high degree of precision is thus made mandatory, not only in the installation of the infrared emitting sources and the associated intensity controls, but also in the temperature stability of the air flow circulating through the oven.

Tests have demonstrated the harmful effect of any temperature variation of this air flow, in particular on thickness distribution and, more generally, on the quality of the final article. This air, which is drawn from the shop where the machine is installed, such shop not normally being equipped with an expensive airconditioning unit, undergoes temperature changes from summer to winter, from day to day, and as a function of parameters such as the opening of a door, for example. In fact, it appears that, during the course of one day, temperature variations may be significant. Since the regulation circuit adjusting the thermal preform processing is controlled by an infrared pyrometer which measures the temperature of the outer walls of the preforms, any temperature variation of the flow of cooling air will affect the temperature of outer preform walls. The relationship obtaining between the quantity of heat stored in the preforms and the reading of the infrared pyrometer will then be distorted. As a result, the regulation of the thermal treatment is disrupted and the exact adjustments of the preform heating profiles are no longer correct, thereby leading to the manufacture of hollow bodies of disparate quality.

SUMMARY OF THE INVENTION

A purpose of this invention is thus to overcome the difficulties mentioned above, and to provide a method and an apparatus which allow the industrial production of hollow bodies made of thermoplastic materials exhibiting uniform quality, despite variations in the ambient temperature prevailing in the production shop.

To this end, the invention provides a method for thermal treatment of preforms made of thermoplastic materials, in particular PET, intended for the manufacture of hollow bodies, such as bottles, flasks, or similar objects, by blow molding or stretch blow molding; in which the preforms rotating on themselves (about their axes) are heated as they travel in front of elements which heat by infrared radiation, a flow of cooling air being used to carry away the excess heat generated by the infrared radiation. The temperature of the flow of cooling air is kept constant and equal to a temperature Tc by mixing air at ambient temperature and hot air, the latter being obtained by recycling at least a part of the flow of cooling air which has become heated by drawing away the excess heat.

The invention also provides an apparatus for the thermal treatment of preforms made of PET designed for the manufacture of hollow bodies such as bottles, flasks, or similar objects, by blow molding or stretch blow molding; blowing or blowing-stretching, comprising rotating preform supports which travel in front of elements which heat by infrared radiation, insulation panels positioned behind these heating elements, reflectors positioned opposite the heating elements, preform-neck protectors, and at least one fan which generates a flow of cooling air used to evacuate the excess heat generated by the infrared radiation, while it cools the components of the apparatus. Means are included for recycling the flow of cooling air which has become heated by evacuating the excess heat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a transverse cross-section of an embodiment of a thermal preform-treatment oven according to the invention, and

FIG. 2 is an example of an ambient temperature curve, as a function of time, for a typical container-production shop.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

According to conventional technique, the preforms are heated in continuous-run ovens equipped with infrared radiation lamps arranged along the path followed by the preforms, which are, in addition, rotated around their longitudinal axes so as to be uniformly heated. The parts of the oven most exposed to the infrared radiation are cooled by a flow of air which evacuates the excess heat.

This process, as specified by the invention, for heating preforms made of thermoplastic materials in order to transform them subsequently into containers, such as bottles, flasks, or similar articles by blow molding or stretch blow molding is implemented in a thermal treatment oven as illustrated in FIG. 1.

Reference numeral 1 designates a preform(s) made of a plastic material, in particular PET and having a sealed end and an open end at the threaded neck 2. These preforms are produced conventionally, e.g., by molding or injection. They are positioned vertically on supports 3 which rotate around their vertical axes X--X, the sealed ends pointing upward.

The supports 3 ar guided laterally by rollers 4 engaged in horizontal, parallel runways 5, and travel into the oven perpendicular to the plane of the Figure. Heating elements 6, such as infrared radiation lamps, are positioned parallel to the path taken by the preforms 1. The number of these lamps depends on the length of the body of the preforms. In the embodiment illustrated, there are eight lamps. Panels 7 made of an insulation material are placed behind the heating elements. Set opposite the panels are reflectors 8 formed, for example, by metal plates whose sides facing the heating elements are polished. The heating elements 6, the panels 7 made of an insulation material, and the reflectors 8 are parallel.

Water-cooled protectors 9 are positioned perpendicular to the lower ends of the insulation panels 7 and the reflectors 8. They are separated from each other so as to allow, with slight play, the passage of the preform bodies. These protectors prevent the necks 2 from being heated by the infrared radiation emitted by the heating elements 6. In fact, the necks, which have already been molded to their final shape and dimensions, must not be significantly heated in order to prevent any undesirable deformation.

The insulation panels 7, the reflectors 8, and the protectors 9 thus form a passageway open at the top and having a slot in its bottom part, delimited by the protectors 9. The preform bodies, which project into the passageway through this slot, travel in front of the heating elements 6 while turning around their axes X--X, so as to ensure uniform heating.

A fan 10 turning around a vertical axis X'--X' draws in air through an air intake or duct 11 and drives it upwards through a guide deflector 12 such that the air circulates in an ascending flow into the passageway delimited by the panels 7, the reflectors 8, and the protectors 9. As a function of the length of the thermal treatment oven, one or several fans can be installed.

A plenum box 12 extends over the length of the thermal treatment oven and is laterally mounted thereon. At its top, it is fitted with a panel 14 which is pivotable around an axis perpendicular to the drawing, as indicated by the chain line. In its lower portion, the box 13 is connected by one of its faces to the air intake 11 of the fan. An opening 15 facing the air intake is formed on the opposite face of the box. A shutter 16 pivotable around a horizontal axis and driven by a motor 18 can seal the opening 15 partially or completely. The amplitude of the pivoting motion of the shutter is such that, in its end positions, it can seal either the opening 15 or an opening 17 located in the lower part of the plenum box and extending over its entire length. It may, moreover, occupy all intermediate positions between the end positions, as shown in FIG. 1. It is evident that, when several fans are installed, there are as many air intakes 11 and openings 15 as there are fans.

A temperature sensing probe 19 is mounted in the air intake of the fan, within the flow of suctioned air, and is connected to a regulation device 20 which controls the pivoting action of the shutter 16 in one direction or another, by means of the motor 18.

In operation, the preforms 1 to be heated are placed on the rotating supports 3 and travel while turning on their axes in front of infrared radiation heating elements 6. The fan 10 draws in a mixture of hot air and air at ambient temperature. The hot air is the air that has circulated in ascending flow in the passageway delimited by the panels 7 and the reflectors 8 and which has been heated by evacuating the excess heat generated by the infrared radiation on the components of the thermal treatment oven. This air is recycled partially or completely through the plenum box 13, and exits through the opening 17. The air at ambient temperature is drawn from the shop where the thermal treatment oven and the associated blow molding or stretch blow molding machine are installed. The pivoting shutter 16 makes it possible to adjust the proportions of recycled hot air and air at ambient temperature in the flow of air drawn in by the fan 10.

A reference temperature Tc is instructed into and/or established by the regulation device 20. The temperature Ts of the air drawn in by the fan and sensed by the probe 19 is continuously compared to the reference temperature Tc. If Ts is greater than Tc, the shutter 16 is moved angularly to reduce the flow of recycled hot air and to increase the flow of the air at ambient temperature. If Ts is less than Tc, the shutter 16 is moved angularly to increase the flow of recycled hot air and reduce the flow of the air at ambient temperature. When Ts =Tc, the shutter 16 maintains its position.

The pivoting panel 14 can also be shifted angularly to regulate the proportion of recycled hot air. In the position shown in solid lines in FIG. 1, most of the hot air will be recycled, while, in the position indicated by the chain line, only a small portion of this air will be recycled.

The advantages offered by the invention include the following:

Whatever the ambient temmperature prevailing in the shop, the temperature of the air forced upward by the fan remains constant. Accordingly, the preform heating conditions remain constant and it is not necessary to adjust the power of the infrared radiation heating elements 6 as a function of ambient temperature in the shop, which may vary significantly during the course of one day, as shown by the experimental temperature curve in FIG. 2. On this curve, hours are shown along the abscissa, and the ambient temperature recorded at the opening 15 is shown on the ordinate. It is apparent that, between 8:00 am and 7:00 pm, the ambient temperature in the shop varied by 11 C., rising from 26 C. to 37 C. In this case, by setting the reference temperature at 37 C. and, because of the device according to the invention, it will not be necessary to adjust the power of the heating elements 6 during the day.

In the winter, the start-up of the manufacture of hollow bodies at the beginning of the week in a shop which has not been heated during non-work days at the end of the preceding week, occurs under favorable conditions, without having to modify or adjust the infrared emitting sources. At the start of the day, the air drawn in by the fan will be made up, for the most part, by hot air recycled through the box 13. As the ambient temperature of the shop rises, the proportion of recycled hot air will decrease. The temperature of the flow of air driven upward by the fan will thus be constant.

Adjustments of the power of the infrared heating elements, which allow preform heating producing blown hollow bodies whose thickness distribution proves satisfactory, may be made in the factory, prior to delivery of the machine and based on the spot where it will be installed. In fact, if the machine is to be installed in a shop whose maximum temperature reached during the year is, for example, 30 C., the reference temperature Tc will be set at 30 C. and the adjustment of the heating elements will be made under these conditions. Accordingly, the machine will immediately be ready for production as soon as its installation in the workshop is completed.

A high degree of uniformity will be obtained in the production of hollow bodies molded from heated preforms. In fact, the thermal treatment of the preforms is made precise, repeatable, and independent of the ambient temperature of the shop in which the thermal treatment oven and the associated blow molding or stretch blow molding machine are installed.

The adjustment of the temperature of the air fed into the thermal treatment oven is obtained using a single energy source, i.e., the heated air which has cooled the oven components. To ensure this adjustment, it is only necessary that the reference temperature Tc be set equal to the maximum ambient temperature reached in the shop.

The reference temperature Tc can be set to the maximum value reached by the ambient temperature during the course of the day, the week, the month, or the year.

The temperature of the cooling air will remain constant despite an abrupt variation of the ambient temperature caused, for example, by opening a door, by a rain shower, a transient period of sunshine, etc.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4050887 *Nov 4, 1974Sep 27, 1977Monsanto CompanyMethod and apparatus for temperature conditioning parts
US4076071 *Oct 22, 1974Feb 28, 1978Heidenreich & Harbeck Zweigniederlassung Der Gildemeister AgMethod for heating plastics materials
US4079104 *Apr 16, 1976Mar 14, 1978Owens-Illinois, Inc.Method for heating plastic articles
US4117050 *Oct 1, 1976Sep 26, 1978Gildemeister Corpoplast GmbhMethod for heating and blow molding plaster parisons
US4234297 *Jan 9, 1979Nov 18, 1980Owens-Illinois, Inc.Apparatus for blow molding
US4300880 *May 30, 1980Nov 17, 1981Yoshino Kogyosho Co., Ltd.Orientation-blow molding equipment and jig used therefor
US4606723 *Mar 28, 1985Aug 19, 1986SidelMethod and apparatus for heating thermoplastic bottle preforms
US5066222 *Mar 14, 1990Nov 19, 1991Bekum Maschinenfabriken GmbhMethod and apparatus for heating and conveying plastic preforms prior to mold blowing operations
DE3101282A1 *Jan 16, 1981Aug 26, 1982Krupp Corpoplast MaschProcess and device for blow moulding hollow articles, in particular bottles
GB2015920A * Title not available
GB2156732A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5549468 *Oct 19, 1994Aug 27, 1996Constar Plastics Inc.For use in an oven of a blow molding machine
US5607706 *Apr 5, 1995Mar 4, 1997Husky Injection Molding Systems Ltd.Preconditioning preforms on a reheat blow molding system
US5641451 *Mar 14, 1995Jun 24, 1997Nissei Asb Machine Co., Ltd.Method for forming heat-resistant containers
US5688466 *Mar 22, 1996Nov 18, 1997Constar Plastics, Inc.Alignment assembly for heating lamps of a blow molding apparatus and method of use
US5714109 *Apr 12, 1996Feb 3, 1998Graham Packaging CorporationMethod and apparatus for supplying conditioned air to a blow-molding oven
US5718853 *Apr 5, 1996Feb 17, 1998Husky Injection Molding Systems Ltd.Preconditioning preforms on a reheat blow molding system
US5780069 *Apr 14, 1995Jul 14, 1998Frontier, Inc.Blow molding apparatus having radiant heating means for preforms
US5866175 *Aug 1, 1997Feb 2, 1999Latham; Greig S.Stretch blow molding machine monitoring system
US6109907 *Mar 31, 1998Aug 29, 2000Takada; MinoruInjection stretch blow molding apparatus with preform heating and guide member
US6186760Feb 1, 1999Feb 13, 2001Greig S. LathamBlow mold machine monitor and control system
US6247916 *May 11, 1999Jun 19, 2001Nissei Asb Machine Co., Ltd.Injection stretch blow molding apparatus with upright preform molding and inverted blow molding
US6444159May 4, 1999Sep 3, 2002Sidel, Inc.Cooling circuits
US6447281Sep 10, 1999Sep 10, 2002Sidel, Inc.Blow mold shell and shell holder assembly for blow-molding machine
US6576872 *Oct 17, 2001Jun 10, 2003Dayco Fluid Technologies S.P.A.Oven for continuous curing of a succession of pre-formed elastomer articles, in particular tubes
US6632087Oct 26, 2000Oct 14, 2003Sipa S.P.A.Infrared heating oven for the conditioning of plastic preforms
US6888103May 30, 2002May 3, 2005Ball CorporationPreform preheater
US7033160 *May 28, 2002Apr 25, 20063D Systems, Inc.Convection cooling techniques in selective deposition modeling
US7220378Jan 7, 2004May 22, 2007Pressco Technology Inc.Method and apparatus for the measurement and control of both the inside and outside surface temperature of thermoplastic preforms during stretch blow molding operations
US7284778 *Feb 14, 2000Oct 23, 2007SidelDevice for carrying preforms comprising improved gripping means
US7425296Dec 3, 2004Sep 16, 2008Pressco Technology Inc.Method and system for wavelength specific thermal irradiation and treatment
US7427374Oct 20, 2004Sep 23, 20083D Systems, Inc.Convection cooling techniques in selective deposition modeling
US7448866Nov 19, 2004Nov 11, 2008Sidel ParticipationsPreform heating module equipped with aerodynamically profiled air baffle
US7491358Mar 12, 2002Feb 17, 2009Sig Corpoplast Gmbh & Co. Kg.Method and device for regulating the temperature of parisons
US8083512Oct 25, 2007Dec 27, 2011Sidel ParticipationsFurnace and equipment for producing sterile vessels from decontaminated preforms of a thermoplastic material
US8167601Feb 18, 2008May 1, 2012Toyo Seikan Kaisha, Ltd.Blow molding machine with air conditioning
US8182094 *Dec 6, 2007May 22, 2012Samsung Electronics Co., Ltd.Light source unit and image projection apparatus having the same
US8257073Nov 30, 2009Sep 4, 2012Sidel ParticipationsOven for the thermal conditioning of preforms, comprising a ventilation plenum
US8287270Sep 30, 2009Oct 16, 2012Printpack Illinois Inc.Methods and systems for thermoforming with billets
US8303290 *Apr 30, 2009Nov 6, 2012Sidel ParticipationsMethod and installation for the production of containers
US8354051Sep 16, 2009Jan 15, 2013Sidel ParticipationsMethod and installation for the production of containers
US8546277Feb 7, 2008Oct 1, 2013Sidel ParticipationsHeating plastics via infrared radiation
US8662872 *Oct 13, 2009Mar 4, 2014Sidel ParticipationsOven for the thermal conditioning of preforms made of a thermoplastic material
US8662876Jun 10, 2008Mar 4, 2014Sidel ParticipationsInstallation for heating the bodies of preforms for blow-moulding containers
US8753106Oct 15, 2012Jun 17, 2014Printpack Illinois, Inc.Billet carrier assembly
US20110203579 *Oct 13, 2009Aug 25, 2011Sidel ParticipationsImproved oven for the thermal conditioning of preforms made of a thermoplastic material
CN100478158CNov 19, 2004Apr 15, 2009西德尔合作公司Preform heating module equipped with an aerodynamically profiled air baffle and oven comprising at least one such module
EP0835736A2 *Oct 6, 1997Apr 15, 1998Nissei Asb Machine Co., Ltd.Stretch blow molding apparatus and injection stretch blow molding apparatus
EP1095757A2 *Oct 6, 1997May 2, 2001Nissei Asb Machine Co., Ltd.Stretch blow molding apparatus
EP2116353A1 *Feb 18, 2008Nov 11, 2009Toyo Seikan Kaisya, Ltd.Blow molding machine with air conditioning
EP2345333A2Dec 5, 2005Jul 20, 2011Pressco Technology, Inc.A method and system for cooking, heating, or processing food
EP2345482A2Dec 5, 2005Jul 20, 2011Pressco Technology, Inc.A method and system for wavelength specific thermal irradiation and treatment
EP2345521A2Dec 5, 2005Jul 20, 2011Pressco Technology, Inc.A method and system for wavelength specific thermal irradiation and treatment
WO2000048819A1 *Feb 14, 2000Aug 24, 2000Sidel SaDevice for carrying preforms comprising improved gripping means
WO2001049075A1 *Oct 26, 2000Jul 5, 2001Alberto ArmellinImproved infrared heating oven for the conditioning of plastic preforms
WO2002087850A1 *Mar 12, 2002Nov 7, 2002Matthias GernhuberMethod and device for regulating the temperature of parisons
WO2005068161A1 *Nov 19, 2004Jul 28, 2005Christophe DoudementPreform heating module equipped with an aerodynamically profiled air baffle and oven comprising at least one such module
Classifications
U.S. Classification264/410, 432/42, 264/40.6, 425/174.4, 432/10, 264/37.17, 425/526, 264/535, 432/21
International ClassificationB29B13/04, B29C49/64, B29K67/00, B29C35/08, B29B13/08, B29B13/02, B29L22/00, B29C49/06, B29C49/00, B29C49/68
Cooperative ClassificationB29C49/68, B29L2031/7158, B29B2911/14593, B29C49/6409, B29C2035/0822, B29C49/06, B29K2067/00
European ClassificationB29C49/68, B29C49/64B
Legal Events
DateCodeEventDescription
Nov 30, 2005FPAYFee payment
Year of fee payment: 12
Sep 27, 2001FPAYFee payment
Year of fee payment: 8
Sep 30, 1997FPAYFee payment
Year of fee payment: 4
Apr 2, 1993ASAssignment
Owner name: SIDEL, FRANCE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:EMMER, GERARD;REEL/FRAME:006525/0473
Effective date: 19930330